In modern warfare, soldiers are often required to fire at both long and short-range targets interchangeably and at a rapid pace. This introduces challenging requirements on the choice of a suitable optical sight. For close quarter combat, the U.S. military utilizes the M68 reflector sight. The M68 which is also known as Close Combat Optic (CCO) can be used with both eyes open which results in quick target acquisition and greater situational awareness. Reflector sights, which are also known as reflex sights or red-dot sights, have no magnification and are unsuited for engaging targets beyond 100 m. For open terrain warfare, the US military uses the M150 telescopic sight also known as the Advanced Combat Optical Gunsight (ACOG). The ACOG is a fixed-power telescopic sight with a bullet-drop compensating reticle specifically designed for the US Army's M4 weapon system. While providing means for accurate aiming at distant targets, the ACOG is not suited for urban environments due to its relatively narrow field of view and limited eye relief.
To overcome the above limitations, some military units have furnished their battle rifles with a combination sight. A combination sight is constructed by attaching a non-magnifying sight such as a red-dot sight to a telescopic sight. The Hensoldt Dual Optic sight used by the German army is an example of a combination sight. Used on the German military G36 battle rifles, the Hensoldt Dual Optic sight combines a telescopic sight with 3× power and a reflector sight mounted on top of the telescopic sight. The reflector sight is calibrated for aiming at 100 m. The reflector sight is illuminated by ambient light during the day and uses battery powered illumination for use at night. The reticle in the 3× telescopic sight is designed for firing at 200 m and has bullet drop compensation markings for: 200, 400, 600 and 800 m.
A combination sight enables a solder to aim at both long-range and short-range targets interchangeably and at a rapid pace. However, this configuration results in a major ergonomic problem: the telescopic sight and the reflector sight require two separate head positions on the rifle. This problem has been noticed by the designers of optical weapon sights and several solutions have been suggested. Some representative prior art are reviewed below.
U.S. Pat. No. 5,349,469 issued to Melvin Francis on Sep. 20, 1994 discloses a combination sight consisting of a high-power telescopic sight and a low-power telescopic sight. This solution uses a tilted erecting prism to incline the viewing axis of one of the telescopes. This makes it possible to position the exit pupils of the two telescopic sights close to each other. While an elegant solution, this design can only be applied to telescopic sights which use a prismatic image erecting system. Variable-magnification (zoom) telescopic sight which are the most common type of telescopic sights use a lens-based erector system, therefore the solution described in this patent is not applicable to them. Another problem associated with this solution is that it requires tilting the entire eyepiece assembly of one of the telescopic sights. Tilting the entire eyepiece assembly imposes a multitude of geometrical restrictions on the size of the optical elements that comprise the eyepiece.
U.S. patent application Ser. No. 13/843,445 filed by Quint Crispin on Mar. 15, 2013 discloses a telescopic sight which features a zig-zag optical path to facilitate mounting it together with a reflector sight. In this solution, the objective lens of the telescopic sight is positioned on the side of the weapon. This causes alignment problems when the sight is to be provisioned with a trajectory-compensating reticle. In addition, this solution has an unwieldy zig-zag shape which is mountable only on certain type of rifles.
U.S. patent application Ser. No. 14/036,325 filed by Stanislaw Szapiel on Sep. 25, 2013 describes a reflector sight equipped with a pair of Risley prisms such that the viewing axis of the reflector sight cab be inclined towards the viewing axis of a telescopic sight. The inclined viewing axis allows a soldier to view the sight image of the reflector sight and the telescopic sight from a single head position. This is an interesting solution but it undermines the principal advantage of the reflector sight: since the view through the reflector sight is deviated, it will not be possible for the human brain to merge it with the view from the unaided eye. Accordingly, the sight described by Szapiel is unsuited for close quarter combat where both eyes need to be open.
What is needed is an ergonomic combination sight which does not require a soldier to change his head position, is easy to mount and can be used with both eyes open. The present invention introduces a combination sight that fulfils these requirements without the limitations associated with the prior art mentioned above.